There has been known a cooling device having an evaporator configured to boil a refrigerant by heat transferred from a heating element such as an electronic device, a condenser configured to exchange heat with ambient air, and piping connecting the evaporator and the condenser to each other. Such a cooling device is disclosed in for example, Japanese Laid-open Patent Publication No. 2013-243277 or Japanese Laid-open Patent Publication No. 2011-163751.